I open the details for all 3 transactions, each has inputs and outputs
There's one output in transaction 3 (Unconfirmed) is the same as one input in transaction 1(Unconfirmed Parent)
There's one output in transaction 1 (Unconfirmed Parent) is the same as one input in transaction 2(Unconfirmed Parent)
What are the relationship of these 3 transactions ?
Transaction 3 -> Transaction 1 -> Transaction 2.
For transaction 1 to have a confirmation, transaction 3 has to confirm first. Afterwhich, for transaction 2 to confirm, transaction 1 has to have a confirmation first.
What kind of transaction are these for; for a payment, a transfer to someone, a transfer to yourself? You can choose to create yet another transaction(which is mentioned above) or to have a replace-by-fee on transaction 3 which will invalidate transaction 1 and 2. Afterwhich, you can choose to create a new transaction that is similar to transaction 3 and continue with transaction 1 and 2.
Replace-by-fee is cheaper than CPFP.